Railroad ballast cleaning machinery is well known in the art. These machines take up the ballast from the track bed clean the ballast, return the cleaned material to the track, and discard the "dirt" or waste contaminating material. One reason for cleaning the ballast is to provide cleaner ballast which can drain water away from the railroad cross ties in order to ensure a longer "life" for the ties. Over a period of time, the track bed becomes contaminated by mud working its way up from underneath, by dirt getting into the ballast from the top, or by the ballast being slowly ground into small particles by vibration caused as trains pass over the ballast. The ballast becomes so contaminated after a period of time that moisture is held around the ties, thus resulting in deterioration of the ties, which results in expensive tie replacement becoming necessary. Thus periodic ballast cleaning is necessary to ensure good drainage. A further disadvantage of contaminated ballast is that the track tends to settle in muddy spots, thus destroying the alignment (line) and surface of the rails.
Some types of ballast cleaners are disclosed in U.S. Pat. Nos. 4,705,115, issued on nov. 10, 1985, to John B. Whitaker, Jr.; 4,850,123, issued on Jul. 25, 1989, to John B. Whitaker, Jr.; 4,534,415, issued on Aug. 13, 1985, to Josef Theurer; and 4,813,488, issued on Mar. 31, 1989, to Josef Theurer. Typically, there are two types of ballast cleaners. One type simply takes up the ballast along the track shoulders (outside the ends of the cross ties) and is known as a "shoulder cleaner." The second type takes up the material underneath and between the cross ties and is known as an "undercutter cleaner."
Normally, a shoulder cleaner utilizes a rotating "ditcher wheel" on each side to take the ballast up from the track shoulder while an undercutter uses a continuous cutter chain to pull the material from underneath the track.
Two of the above-identified patents (4,534,415 and 4,813,488) relate to an undercutter type of apparatus which utilizes a chain-type excavator which requires that the track be raised for the excavation of the ballast. After the ballast cleaning operation is completed, the tracks must be levelled in an attempt to restore the original track line.
A typical ballast reconditioning apparatus which uses a ditcher wheel and undercutter configuration is disclosed in U.S. Pat. No. 4,850,123. The patent is directed to a pair of rotatable undercutters and means for raising, lowering, and horizontally moving the undercutters. The patent also discloses a ditcher wheel mounted forwardly of the undercutters to remove ballast from the shoulders of the railroad bed and a single cleaner screen for cleaning the ballast. In this type of apparatus, forward progress is limited by the speed at which the ballast can be cleaned by the single screen cleaner. Furthermore, the contaminated ballast removed by the undercutter is deposited at the shoulders of the railroad bed (uncleaned) while the ballast removed from the shoulders of the bed by the ditcher wheels are transported to a single cleaning station having a vibrating screen assembly therein. If it is desirable to remove the uncleaned deposited ballast from the shoulders for cleaning, it is necessary for the ditcher wheels to be raised so that the apparatus can be reversely moved over the excavated area of the railroad bed and another pass made to pick up the deposited ballast from the shoulders by the ditcher wheels.
As can be seen, the production rate of such apparatus is unduly restricted if all of the excavated ballast is to be reconditioned. The rate and amount of ballast cleaning is severely limited since only a single cleaning station is provided. Also, the requirement for repeated passes over the area to recondition all of the excavated ballast is time consuming (and costly).
U.S. Pat. No. 4,705,115 discloses a ballast reconditioning system having two ditcher wheels, one on each side of the vehicle frame, and an undercutter mounted rearwardly of each ditcher wheel to remove ballast from beneath the tracks. The ballast removed from the shoulders of the railroad bed by the ditcher wheels is transported rearwardly of the undercutter to be directly discharged (without cleaning) onto the center of the track to replace the ballast removed by the undercutter. The apparatus of U.S. Pat. No. 4,705,115 uses conveyor belts to transport the ballast picked up by the ditcher wheels to the rear of the undercutter and onto the center of the track and also to transport the ballast picked up by the undercutter to the single ballast screen cleaner. A clean ballast return receives the cleaned ballast and returns it to the shoulders of the railroad bed.
The forward speed of the apparatus is severely limited since only a single ballast screen is provided for cleaning the ballast picked up by the undercutter device. Furthermore, it should be noted that the shoulder ballast which is returned (uncleaned) to the center of the track still contains a large amount of contaminants such as mud, small dust particles, etc., and will not provide the high degree of drainage afforded by a track bed having clean shoulder ballast. As a result of not cleaning all of the excavated ballast in a single operation, more frequent periodic maintenance of the railroad track is required.
Structure is disclosed in our U.S. Pat. No. 5,029,649, issued Jul. 9, 1991 (incorporated herein by reference), which is directed to a ballast reconditioning system which uses two discrete pairs of ditcher wheels and an associated single cleaning station for the ballast picked up by each pair of ditcher wheels. Such structure, while more efficient than heretofore known systems, still has the defect of being slowed down because of the cleaning limitations imposed by the use of a single cleaning station for each pair of ditcher wheels.
Apparatus of the present invention overcomes the noted difficulties by providing a ballast system which uses two pairs of ditcher wheels to pick up ballast from a railroad track and four cleaning stations. Each ditcher wheel is provided with its own cleaning station and means for transporting the cleaned ballast back to the railroad bed. Additionally, an undercutter device for cleaning ballast from beneath the tracks is provided intermediate the ditcher wheels of each pair of ditcher wheels. One pair of ditcher wheels and an undercutter device are mounted on a first side of a vehicular frame, and the second pair of ditcher wheels and the second undercutter are mounted on the opposite side of the vehicular frame. Conveyor systems carry the dirty ballast to the cleaning stations and also convey the cleaned ballast back onto the railroad bed.